A NOVEL RADIOIMMUNOASSAY OF ALLOPREGNANOLONE

A radioimmunoassay for determination of 3 alpha-hydroxy-5 alpha-pregna n-20-one (allopregnanolone) in serum or plasma has been developed and evaluated. The method employs rabbit antiserum to 3 alpha-hydroxy-5 al pha-pregnane-11,20-dione-11-O-carboxymethyloxime bovine serum-albumin conjugate and tritiated radioligand. The main cross-reactant interferi ng in the assay, progesterone, is eliminated by permanganate oxidation . Two assay variants were compared, with and without a micro-column ch romatography. The simplified variant appeared to be reliable enough fo r determination of allopregnanolone in normally menstruating women at luteal phase, whereas the column-chromatography step is necessary when analyzing samples of expected low analyte concentration as in women i n follicular phase, postmenopausal women, or in men. The levels of all opregnanolone in healthy women correlated excellently with progesteron e in agreement with previous findings.